1. Field
One or more exemplary embodiments relate to a thermoelectric material and a chalcogenide compound, and more particularly, to a thermoelectric material and a chalcogenide compound both having low thermal conductivity and a high Seebeck coefficient.
2. Description of the Related Art
In general, thermoelectric materials are used in active cooling, waste heat power generation, and other similar applications of the Peltier effect and the Seebeck effect. FIG. 1 is a schematic diagram illustrating thermoelectric cooling using the Peltier effect. Referring to FIG. 1, the Peltier effect is a phenomenon whereby, when a DC voltage is externally applied, holes of a p-type material and electrons of an n-type material are transported to cause heat absorption at one side of both the p-type and n-type materials. FIG. 2 is a schematic diagram illustrating thermoelectric power generation using the Seebeck effect. Referring to FIG. 2, the Seebeck effect is a phenomenon whereby, when heat is supplied from an external heat source, current-flow is generated in the material while electrons and holes are transported to cause power generation.
Active cooling that uses such a thermoelectric material improves thermal stability of devices, does not cause vibration and noise, and does not use a separate condenser and refrigerant, and the active cooling method is environmentally-friendly. Thus, active cooling that uses such a thermoelectric material may be applied to refrigerant-free refrigerators, air conditioners, a variety of micro cooling systems, and the like. In particular, when a thermoelectric device is attached to memory devices or other computer devices, the temperature of the devices may be maintained to be uniform and stable, especially in comparison with a conventional cooling method. Thus, the memory device or other computer device can have improved performance.
Meanwhile, when thermoelectric materials are used in thermoelectric power generation using the Seebeck effect, the waste heat is extracted and transformed to electrical energy by the thermoelectric materials. Thus, thermoelectric materials may be applied in a variety of fields that increase energy efficiency or reuse waste heat, such as in vehicle engines and air exhausters, waste incinerators, waste heat in iron mills, power sources of medical devices in the human body using human body heat, and other applications.
A dimensionless figure-of-merit ZT, defined as shown in Equation 1 below, is used to show the performance efficiency of a thermoelectric material.
                    ZT        =                                            S              2                        ⁢            σ            ⁢                                                  ⁢            T                    k                                    Mathematical        ⁢                                  ⁢        Formula        ⁢                                  ⁢        1            
Here, S is a Seebeck coefficient, σ is an electrical conductivity, T is an absolute temperature, and κ is a thermal conductivity of a thermoelectric material.
To increase values of the dimensionless figure-of-merit ZT, there is a need to develop a material having a high Seebeck coefficient and high electrical conductivity and low thermal conductivity.